1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a semiconductor device including a metal-insulator-metal (MIM) capacitor and a method of manufacturing the semiconductor device.
2. Description of the Related Art
In recent years, lowering of a dielectric constant (attaining of low-k) of a wiring interlayer insulating film has been advanced. It is anticipated that low-k films will be used for almost all wiring layers in the future. However, in general, the low-k films have high porous property, and in proportion to that, have high hygroscopicity. Such properties described above become more apparent in ultra low-k films having a specific dielectric constant value “k” which falls below 2.5. When a MIM capacitor is mounted between interlayer insulating films, concerns about influence of moisture which has been absorbed in the interlayer insulating films are raised. The influence of moisture may cause problems such as reliability degradation in dielectric films, deterioration in polarization characteristics, and oxidation of electrode materials.
JP 2006-202848 A discloses the structure including a ferroelectric capacitor which is formed in the same layer together with a contact layer or a MOS transistor layer provided on a semiconductor substrate. In the structure described above, the ferroelectric capacitor is formed on an antioxidant film and a hydrogen barrier metal film is formed so as to cover the ferroelectric capacitor.
When the MIM capacitor is formed in the contact layer or the MOS transistor layer below a wiring layer, the antioxidant film and an alumina film with moisture resistance are required to be separately formed immediately below the MIM capacitor in the conventional technology. Further, compared with the process of manufacturing a semiconductor device which is not provided with the MIM capacitor, the process in this case causes a larger height difference between contacts, and hence it is difficult to control dimension and size of the contacts. In the structure shown in JP 2006-202848 A, a step between an upper electrode and a lower electrode is caused. Therefore, in a case where an interlayer insulating film is formed by chemical vapor deposition (CVD) or the like, this step portion may lead to degradation in film quality (low density), decrease in film strength, or the like.